The invention relates to a semiconductor device with a semiconductor diode and comprising a semiconductor body with a stack of, in that order as seen from the upper surface of the semiconductor body, a first semiconductor region of a first conductivity type which is provided with a first connection conductor, a second semiconductor region of a second conduction type opposed to the first which is connected to a second connection conductor, while a rectifying junction is present between the first and the second semiconductor region. The invention also relates to a method of manufacturing such a device.
Such a device is widely used, in particular as a discrete component, for example as a switching diode, in particular for switching a high voltage, which in practice often implies switching a high power. It is important in practice that the discrete component should be suitable for surface mounting in view of the ever continuing miniaturization.
A device of the kind mentioned in the opening paragraph is known from U.S. Pat. No. 5,164,813 published Nov. 17, 1992. A mesa-shaped diode is described therein (see FIG. 15) with an n-type epitaxial layer in which a p-type diffusion region is formed. A rectifying junction is present therebetween. The p-type diffusion region is connected to a p+-type substrate lying on the surface of the semiconductor body. Metal plates are present on this substrate and on the n-type substrate, which plates form the connection conductors of the diode, whose flanks are passivated. This construction renders the diode suitable for surface mounting. In fact, the diode can be mounted, for example on a PCB (Printed Circuit Board) after rotation through 90xc2x0 with respect to the orientation shown in FIG. 15, such that the lateral sides of the connection conductors can be directly fastened to conductor tracks of the PCB, for example by soldering.
A disadvantage of the known diode is that it is found to be insufficiently reliable, in particular if it is designed for high powers and if the pn junction is tangent to the edges of the mesa-shaped semiconductor body of the diode. Thus breakdown may occur along the lateral side of the mesa, or an unacceptably high leakage current, in the case of a high operating voltage, which is often accompanied by a high power dissipation.
It is an object of the present invention, therefore, to provide a diode which does not have the above disadvantage, or at least to a much lesser degree, and which is suitable for high-voltage applicationsxe2x80x94also at high power levels, and for surface mounting. At the same time, the manufacture of the diode should be simple and inexpensive.
According to the invention, a device of the kind mentioned in the opening paragraph is for this purpose characterized in that a portion of the first semiconductor region is electrically insulated from the rest of the first semiconductor region, the semiconductor body is provided with means by which said portion of the first semiconductor region is conductively connected to the second semiconductor region, and the second connection conductor is present on said portion of the first semiconductor region. The invention is based on the following surprising recognitions and measures. Insulation of a portion of the first semiconductor region from the rest of this region renders it possible to realize an attractive connection configuration of the diode. Since the device according to the invention is provided with means by which the separated portion of the first semiconductor region is connected with electrical conduction to the second semiconductor region, the surface of said portion of the first semiconductor region can act as a connection region for the second semiconductor region. For this purpose, the second connection conductor lies on said portion of the first semiconductor region. Both connection conductors now lie at the same side of the semiconductor body, which renders the device suitable for so-called surface mounting. At the same time, the two connection conductors may easily lie at a large distance from one another, because the interspacing of these connection conductors is no longer defined by the thickness of the semiconductor body. This renders a device according to the invention particularly suitable for use at high voltages and/or for a high power dissipation. Furthermore, the device according to the invention is very easy to manufacture, as will be explained in more detail further below.
In a major embodiment, the electrical insulation of said portion of the first semiconductor region from the rest thereof is realized in that a groove is provided in the surface of the semiconductor body. This groove extends to at least beyond the rectifying junction. Such a groove may be very easily provided, may be very easily given the desired, comparatively large width, and may also be easily filled with electrically insulating materials by which the rectifying junction is passivated.
In a preferred embodiment of a device according to the invention, the means by which said portion of the first semiconductor region is connected with electrical conduction to the second semiconductor region comprise a conductive channel formed in the semiconductor material of said portion of the first semiconductor region. An important and surprising recognition for the invention here is that such a conductive channel can be made in a particularly simple manner, i.e. through the supply of an energy pulse, preferably a current pulse, to that portion of the rectifying junction which lies between said portion of the first semiconductor region and the second semiconductor region. A short-circuit between said portion of the first semiconductor region and the second semiconductor region which turns out to be very useful in practice is created thereby in this location. Additional advantages of this are that the application of such a conductive channel does not substantially affect the manufacture of the device and can also take place in an at least substantially final stage of manufacture. Partly as a result of this, the (electrical) testing of the device can take place simultaneously with or at least immediately after the provision of the conductive channel.
In an also particularly favorable modification, said means comprise a hole formed in the semiconductor body at the area of said portion of the first semiconductor region, the wall of said hole being provided with a conductive layer. Since such a hole can be readily provided, for example by etching, laser cutting, or sandblasting, this modification is also very inexpensive in its manufacture, which is a very important aspect in the case of discrete components.
In all cases mentioned above, the dimensions and geometry of the portion of the first semiconductor region and the remaining portion of that region are preferably the same. This also has the result that the manufacture of the device according to the invention is very simple. One could say that one out of every two devices is sacrificed each time in order to achieve the effect envisaged by the invention in the manufacture of a device according to the invention. The disadvantage of the material loss involved therein is surprisingly outweighed by the advantages achieved by the invention in practice. The result, a symmetrical device, is also highly attractive from a final mounting point of view. In addition, a device according to the invention is highly suitable for a so-called CSP (Chip Scale Package) envelope, so that it can still be very compact.
A method of manufacturing a semiconductor device with a semiconductor diode, where a semiconductor body is formed by a stack of, in that order as seen from the upper surface of the semiconductor body, a first semiconductor region of a first conductivity type which is provided with a first connection conductor, a second semiconductor region of a second conductivity type opposed to the first which is connected to a second connection conductor, while a rectifying junction is present between the first and the second semiconductor region, is characterized according to the invention in that a portion of the first semiconductor region is electrically insulated from the rest of the first semiconductor region, and the semiconductor body is provided with means by which said portion of the first semiconductor region is conductively connected to the second semiconductor region. A device according to the invention is obtained in a simple and inexpensive manner by such a method.
Preferably, an interruption is formed in the first semiconductor region in that a groove is provided in the semiconductor body whereby said portion of the first semiconductor region is separated from the rest of the first semiconductor region. Such a method has the advantages discussed above for the modification of the device according to the invention. The same holds for the major advantages of a very favorable modification wherein the means are formed by the provision of a conductive channel in the semiconductor material of said portion of the first semiconductor region through the application of a high-energy pulse, preferably an electric current pulse, to that portion of the rectifying junction which adjoins said portion of the first semiconductor region.
In a modification of a method according to the invention which is also favorable, the means are formed in that a hole is formed in the semiconductor body at the area of the portion of the first semiconductor region, the wall of said hole being provided with a conductive layer. The techniques for making such a hole as mentioned above are particularly simple and inexpensive. The use of a hole has the additional advantage that it is not necessary to ascertain that the rectifying junction has been reached. As was noted above, the geometry and dimensions of said portion and of the remaining portion of the first semiconductor region are preferably manufactured so as to be equal.